This application relates generally to a method and apparatus for removing electrostatic charges from sheets of dielectric material arranged in a stack. Such a method and apparatus are particularly useful for removing the electrostatic charges which may accumulate on sheets of paper during processes such as high speed printing and electrostatic copying.
Certain processes have a tendency to transfer relatively large electrostatic charges to the surfaces of dielectric material. Such surface charges can have the undesirable effect of hindering subsequent attempts to separate or otherwise arrange stacked sheets of the dielectric material. An example of such a problem frequently arises in the fields of electrostatic copying and high speed printing. Paper, emerging from a photocopier or high speed printer, often bears large electrostatic surface charges. Once such paper has been stacked, it is almost impossible to "jog" the edges of the paper into alignment until the accumulated charges have leaked off. This may take hours, or even days, and undesirably prolongs overall processing time.
Many papers, such as fold-form paper passing through a laser printing system, have an extremely strong positive charge. The charge may remain within the stack for hours to days, and greatly hinders subsequent jogging of the papers into alignment since random negative surface charges are imparted to the sheets during handling causing some adjacent sheets to have a strong attraction to each other. According to the present invention, by the application of a high negative potential to the entire stack, electrons are forced into the stack filling the absence of electrons created in previous processing (which created the positive charge). Once the positive charge is eliminated, there are no electrical attractive forces acting between adjacent sheets in the stack. The sheets may then be successfully jogged (in any suitable conventional manner) immediately after treatment, with about a 15% increase in jogging production.
The present invention provides in general a method and apparatus for simultaneously altering accumulated static electric charges on sheets of dielectric material, such as paper, arranged in a stack. This is accomplished in the present invention by subjecting the stack of paper to an extremely strong potential gradient. It has been found that such treatment completely depletes opposite polarity electrostatic charges on the stacked sheets of paper, thus facilitating subsequent handling operations. Treating an entire stack of paper is quicker and more efficient that individually treating separate sheets of paper, and is accomplished simply according to the invention. These and other advantages of the invention will become more readily apparent from the following detailed description of the presently preferred exemplary embodiments, taken together with the accompanying drawing.